The hydrogenation of aromatic hydrocarbons is well-known in the art. It is also known to use catalyst compositions in such hydrogenation processes comprising supported hydrogenating components consisting of at least one member of Group VI-B and at least one member of the Group VIII metals in a form capable of promoting hydrogenation reactions. Especially effective catalysts are those comprising nickel and tungsten. Other catalysts found to be effective include those containing nickel, cobalt and molybdenum, nickel and molybdenum and cobalt and molybdenum. The hydrogenating components of such catalysts can be employed in sulfided or unsulfided form.
Although the hydrogenating components indicated above can be employed in any proportions with each other, especially effective catalysts are those in which the hydrogenating components are those in the group consisting of oxides and sulfides comprising (a) a combination of 5 - 25 percent by weight of a Group VI-B metal and (b) 5 - 20 percent by weight of a Group VIII metal. The hydrogenating components can be composited with a porous alumina support. The alumina support is normally shaped in the form of granules, pellets or balls, prior to compositing the hydrogenating metals therewith. The catalyst composite, however can be in other forms such as a powder which is employed for conventional fluid type operations.
Conventionally, in the preparation of the prior art catalyst composites the hydrogenation component such as tungsten is deposited on the support from an aqueous solution of the salt. After filtering and drying, the impregnate is calcined to convert it into the oxide. Th carrier is then treated with an aqueous solution of the iron group metal salt such as nickel, followed by calcining. If a second iron group metal is employed, the second iron group metal can also be deposited in a like manner. Nitrates or acetates of the iron group metals are normally utilized although any water soluble salt which leaves no harmful residue can be employed.
If desired, the iron group metals and the Group VI-B metal can be deposited simultaneously but are preferably deposited in sequence with intervening calcining. Simultaneous impregnation of the iron group metals has been found to be satisfactory.
Calcining of the catalyst composite can be conducted by heating in air to a temperature of 800.degree. to 1600.degree.F. (427.degree.-871.degree.C.). When a sulfided catalyst is desired, the catalyst prepared as described above can be treated in a known manner with hydrogen sulfide or preferably a mixture of hydrogen and hydrogen sulfide. Typically, the catalyst composite can be presulfided after calcination, or calcination and reduction, prior to contact with the charge stock, by contacting with a sulfiding mixture of hydrogen and hydrogen sulfide. Normally, the sulfiding is conducted at a temperature in the range of 500.degree. to 650.degree.F. (260.degree. to 343.degree.C.) at atmospheric or elevated pressures. Presulfiding can be conveniently effected at the beginning of an onstream period at the same conditions to be employed at the start of the hydrogenation process. The exact proportions of hydrogen and hydrogen sulfide are not critical and mixtures containing low or high portions of hydrogen sulfide can be used. Relatively low proportions are preferred for economical reasons. Elemental sulfur or sulfur compounds, such as mercaptans, can be used in lieu of hydrogen sulfide.
Although the above-identified catalyst compositions are useful in the hydrogenation of petroleum aromatic hydrocarbons, it is desirable to improve the efficiency of such aromatic hydrogenation processes at a given operating temperature and, in some instances, obtain high hydrogenation process conversions at lower operating temperatures.
Accordingly, an object of this invention is to provide an impoved aromatic hydrogenation process.
Another object of the invention is to provide a novel catalyst composition for the hydrogenation of aromatic hydrocarbons.
Yet another object of the invention is to provide a process for the preparation of an improved hydrogenation catalyst composition.
Other objects, advantages and features of the invention will be readily apparent to those skilled in the art from the following description and appended claims.